Simona Halep, the top seed in the Citi Open and the second-ranked women's tennis player in the world, retired from her quarterfinal match Friday because of illness brought on by the heat. Halep was trailing No. 7 seed Ekaterina Makarova, 6-2, 3-6, 1-0, when she called the trainer over early and appeared to have her blood pressure taken, after which she immediately retired. "I had a headache," Halep said, "and little sick, so it was better to stop." The temperature was 90 degrees in Washington at the time of Halep's match on Friday. Makarova, a Russian ranked 58th in the world, advanced to face fifth-seeded Oceane Dodin, who beat Sabine Lisicki, 5-7, 6-4, 7-6 (4), in the semifinals. On the men's side, eighth-seeded Jack Sock upset third-seed Milos Raonic, 7-5, 6-4, to advance to the semifinals. In other men's quarterfinal matches, Kevin Anderson defeated Yuki Bhambri, 6-4, 4-6, 6-3, and fifth-seeded Alexander Zverev beat Daniel Medvedev, 6-2, 6-4. In men's doubles, Mike and Bob Bryan defeated Rohan Bopanna and Donald Young, 7-5, 6-4, to advance to the semifinals, where the fourth-seeded brothers will play the second-seeded pair of Lukasz Kubot and Marcelo Melo.